Preheat the oven to 190°C/375°F/gas 5. Get yourself an appropriately sized roasting tray, large enough to take the tomatoes in one snug-fitting layer. Put in all your tomatoes, the herb sprigs, oregano, garlic and sausages. Drizzle well with extra virgin olive oil and balsamic vinegar and season with salt and pepper. Toss together, then make sure the sausages are on top and pop the tray into the oven for half an hour. After this time, give it a shake and turn the sausages over. Put back into the oven for 15 to 30 minutes, depending on how golden and sticky you like your sausages.